Nitrogen Uptake and Leaching under Annual Bluegrass Ecotypes and Bentgrass Species

Nitrate (NO; ) can leach from golf greens, potentially causing the degradation of surface and ground water quality. A greenhouse experiment was conducted with 11 annual bluegrass (Poa annua var. reptans Hausskn.) ecotypes from eastern Canada (Quebec and Ontario) and the USA, and three bentgrass (Agrostis spp.) species to compare N uptake and potential for N leaching. Two-month-old grasses were established for a 6-wk period in lysimeter columns simulating a golf-green profile. An unplanted root zone control was included. Water-soluble fertilizer was applied at 25 kg N ha -1 (NH 4 NO 3 ) every 14 d for 57 d. Leachate samples were collected every second day and analyzed for NO 3 -N and ammonium N (NH 4 -N) content. Dry weight and N concentration were determined on clippings, shoots, and roots. Ammonium N leaching was negligible for all grasses. Less NO 3 -N leaching losses occurred under bentgrasses (6-11% of applied N) than under annual bluegrasses (28-71% of applied N). Differences in NO 3 -N leaching were also found within annual bluegrasses; Quebec P. annua > Ontario P. annua > USA P. annua. Grasses with a greater aboveground biomass developed a larger and deeper root system and were associated with a greater N uptake (r = 0.94) and, therefore, a lower NO 3 -N leaching (r = -0.94). Breeding programs and management practices to improve turfgrass root development appear to be critical to reduce fertilizer N leaching under sand-based putting greens.